1. Field of the Invention
The present invention relates to an infusion apparatus capable of infusing medication into a patient in a pattern appropriate for the kind of medication and the condition of the patient.
2. Description of the Prior Art
Infusion apparatuses are used for administering medication such as a saline solution into a vein of a patient. A generally known infusion apparatus is of an electromechanical positive pressure peristaltic type provided with a pump mechanism for peristaltically delivering medication. FIG. 6 shows an example of such a pump mechanism. The pump mechanism, generally indicated by numeral 8 in FIG. 6, has n pressure fingers 83(1), 83(2), . . . , 83(n) with their ends 83a(1), . . . , 83a(n) confronting a door 85 of a housing of the infusion apparatus, and n cams 82(1), 82(2), . . . , 82(n) associated with the n pressure fingers 83(1), 83(2), . . . , 83(n). The cams 82(1), 82(2), . . . , 82(n) are engaged with a shaft driven by a not-shown stepping motor, with their phases shifted from one another. The pressure fingers 83(1), 83(2), . . . , 83(n) are individually moved in sequence toward the door 85 by the associated cams 82(1), 82(2), . . . , 82(n) with rotation of the shaft 81 so as to push an administration tube 84 set in the pump mechanism against the door 85. By so pressing the administration tube 84 against the door 85 from above downward with the fingers 83(1), 83(2), . . . , 83(n), medication supplied from an administration set into the administration tube 84 is peristaltically delivered to a patient.
FIG. 7 shows a block diagram of a conventional infusion apparatus of the above-mentioned type, FIG. 9 is a flowchart showing the operation of the infusion apparatus of FIG. 7, and FIG. 10 is a perspective view Showing a part of the infusion apparatus. It is to be noted that because an infusion apparatus of the present invention described later has a similar appearance, FIG. 10 is also used to illustrate the infusion apparatus of the present invention.
Referring to FIG. 7 and FIG. 10, a power switch 1 turns on the infusion apparatus, generally indicated by numeral 100, when pressed. An alarm display unit, designated by numeral 2, displays all alarm messages for errors detected in the infusion apparatus. A display unit, designated by numeral 3, displays infusion-related parameters such as a volume of infusion fluid delivered per unit time (simply referred to as "infusion rate" or "delivery rate" below), a total volume of infusion fluid to be delivered at the infusion rate (simply referred to as "volume to be delivered" or "volume to be infused" hereinafter), as well as an accumulated volume of the infusion fluid already delivered (referred to simply as "accumulated infusion fluid volume" hereinafter). A key panel, designated by numeral 4, has thereon numeral keys for inputting settings such as the infusion rate and volume to be infused or delivered in order to set values of an operation speed and operation time for the pump mechanism 8, control keys for input assistance, a start key for starting the operation of the pump mechanism 8, a stop key for stopping the operation of the pump mechanism 8, and a call key for requesting various values such as the accumulated infusion fluid volume to be displayed. A state indicator, designated by numeral 5, is a lamp that indicates which state the apparatus is currently in among the states of "alarming", "in operation", and "out-of-operation". A door opening detector, designated by numeral 6, detects whether or not the door 85 has come into an open position in which the administration tube 84 is set in place in the pump mechanism 8. The door opening detector 6 also detects that the door 85 is inadvertently opened while the pump mechanism 8 is in operation. When this error is detected, the operation of the pump mechanism 8 is stopped and an alarm is raised. An upstream occlusion sensor, designated by numeral 7, detects a pressure-reduction state caused by occurrence of any abnormality (e.g., clogged filter) in the administration set disposed between a medical fluid container 32 and the apparatus. A motor driving circuit, designated by numeral 9, drives the stepping motor of the pump mechanism 8 in response to a pulse outputted from a CPU 18. A rotation detector, 10 designated by numeral 10, through detection of the amount of rotation of the stepping motor of the pump mechanism 8 detects that an incremental unit (e.g., 1 ml) of fluid has taken place, and then informs the CPU 18 of it. A downstream occlusion sensor, designated by numeral 11, detects a pressure-rise state within the administration tube 84 located between the apparatus and the patient to detect occurrence of any abnormality such as occlusion occurring within the administration tube 84. When the pressure-rise state is detected, the pump mechanism 8 is stopped and an alarm is raised. An air bubble detector, designated by numeral 12, detects that air bubbles of more than a prescribed amount have entered the administration tube 84. When this is detected, an alarm is raised while the pump mechanism 8 is stopped so that the bubbles are prevented from entering into the patient's body. A battery-voltage detector, designated by numeral 13, detects any battery-voltage drop of a lead battery (not shown) used as a backup of an AC power supply. When this battery-voltage drop is detected, operation of the pump mechanism 8 is stopped while an alarm is raised. The lead battery is charged by a power supply circuit 15 when the apparatus is fed power from the AC power supply. A buzzer driving circuit, designated by numeral 14, generates a buzzer sound for informing doctors and nurses of the fact that the infusion apparatus has entered into the alarming state. The power supply circuit 15 supplies power to all the circuits of the infusion apparatus. An analog-to-digital converter, designated by 16, converts analog data such as the voltage resulting from voltage conversion of a current supplied to the motor of the pump mechanism 8, the air bubble detector output level, and the battery voltage level into digital values, and inputs them into the CPU 18. A panel lock switch, designated by numeral 17, serves to render the panel keys and the power key input-inhibited so that the infusion apparatus will not be operated by unauthorized personnel. The CPU 18 controls the operation of the overall infusion apparatus. A RAM (memory section), designated by numeral 19, includes a first storage section 21 for storing an infusion rate and volume to be infused, those parameters having been key-inputted, a second storage section 22 for storing various types of data used for arithmetic operations by the CPU 18. A ROM (program section), designated by numeral 20, contains a program for operating the CPU 18.
FIG. 8 shows an example of a pattern of combination of the infusion or delivery rate and the volume to be infused or delivered (this pattern will be referred to as "delivery pattern" below), which is stored in the first storage section 21 of the RAM 19. In FIG. 8, the infusion rate is plotted on the axis of ordinates and the volume to be infused is plotted on the axis of abscissas. In this case, the infusion rate is 125 ml/hr, and the volume to be infused is 250 ml.
The following describes the operation of the above conventional infusion apparatus with reference to a flowchart shown in FIG. 9.
When the infusion apparatus 100 is turned on at step S1, the apparatus 100 requests an operator, more specifically a doctor or nurse, to input parameter values of the infusion rate and volume to be infused. Therefore, in response to this request, the operator inputs values of the infusion rate Ri and volume to be infused Vi, at step S2, according to the kind of medication to be administered and the therapeutic procedures selected. The pump is started at step S3 when a command to start the pumping operation is key-inputted, the pump mechanism 8 starts to feed an infusion fluid at the inputted infusion rate. Then, at step S4, it is determined whether or not there was an incremental unit of fluid (1 ml in this case), which is detected by the rotation detector 10. If yes, the program proceeds to step S5 at which 1 is subtracted from the initially inputted value of the volume to be infused Vi, and a new value obtained through this subtraction is set as a renewed volume (Vi=Vi-1). Next, at step S6, it is determined whether or not the volume to be infused Vi has reduced to zero. Vi=0 signifies that all the infusion fluid to be infused in this infusion operation has been delivered. Therefore, when it is determined that Vi=0 at step S6, the operation of the pump mechanism 8 is stopped at next step S8. However, even when the remaining volume to be infused Vi is not zero, the pump mechanism 8 is stopped if, at step S7, a corresponding key operation by the operator or an occurrence of some alarm requires stoppage. Then the program returns to step S2 to wait for an input of the next values Ri, Vi of the infusion rate and volume to be infused for the next infusion operation.
The above-mentioned conventional infusion apparatus cannot store more than one delivery pattern as shown in FIG. 8 in the first storage section 21. Some infusion fluids can adversely affect the patient if infused at only a single infusion rate. For example, in some cases, with potent medications, it is desirable to start infusing the medication into the patient little by little at the beginning, then gradually increase the initial infusion rate to a target infusion rate as the patient grows accustomed to the medication, and finally infuse the remaining major part of the medication at the target infusion rate. Also, in some cases, the patient can be adversely affected if infusion is suddenly stopped. This is because the patient's body, into which medication has been infused, cannot quickly adapt itself to the sudden change of condition from the infused state to the non-infused state. In such a case, it is recommendable to gradually reduce the infusion rate to zero in the final stage of the infusion.
However, when such a flexible infusion operation is desired, a single delivery pattern is insufficient. Accordingly, the conventional infusion apparatus having only a single delivery pattern cannot be used to infuse some kinds of medication in some cases, unless the operator, i.e., a doctor or nurse, stays by the apparatus and changes the infusion rate and the volume to be infused.